STUCK ON 5TH GEAR, SLOW ACCEL.

2004 Nissan Maxima • 164,000 miles

Hi my. Name. Is Miguel. I replaced my tranny or better yet rebuilt it with aamco. Approx a year ago and have ran it approx 20000 miles since then. Today on freeway the car gave me a hardshake and stalled I pulled to. The side an turned vehicle back on. It was stuck on 5th gear. It would not down shift and still won't. I stepp on pedal full throttle on it way to.60 it has no prob except it accelerates as if if I was stepping. On pedal 1/5 to 1/4 down check engine drove for ever turned on. Only. Dcause i. Only. Drove for approx 20 more miles thebl last 5 were street. Thanks for any help

Manual or automatic? If it's manual check fluid in trans make sure its 'full. Your shift linkage may be jammed as well causing this or maybe a cable or rod broke. There are two cables that control shifting so have a local pro look at it.